1. Field of Invention
This invention is directed to systems and methods for sensing media size in an image formation device.
2. Description of Related Art
It is important for a printer to recognize the size of the media loaded in the printer that data is to be printed on. Typically, the most basic form of media size sensing is to measure the length of the print media, such as paper, as the media travels through the print path of the printer using position/size sensors. Almost all printers have this form of media length sensing. A problem with detecting only the paper length is that it is assumed that the paper is of a standard size (length and width). It is further assumed that the user knows the width of the media loaded in the printer. However, as there are often many different page sizes that may be sensed, the more sizes the printer is capable of using, the greater the chance the user may incorrectly choose the size of the media loaded in a paper tray of the printer, which can lead to undesired results. For example, choosing an incorrect media size can lead to ink being deposited outside of the boundary of the chosen media.
U.S. Pat. No. 5,940,106 discloses several known methods of determining the width of print media. For example, both reflective photodiode and capacitor sensor methods of media sensing rely on the position of the printer carriage to determine the media width. U.S. Pat. No. 5,940,106 also discloses a resistive sensing system for determining the size of print media loaded in a printer. The system includes sliding mechanical length and width size adjusters within a paper tray into contact with the edges of the print media. These length and width size adjusters each have sliding contacts which engage an energized conductive strip at a location corresponding to the position of the size adjusters. The printer has a controller that interprets an electrical signal received from the sliding contacts to determine the size of the print media loaded into the printer.
In a standard paper tray, multiple sensors with flags are sometimes used. The flags are set by moving side guides, or length backstops in the tray, which have discreet sensor settings for each different media size. Such flag systems function adequately for trays containing standard size paper, such as 8.5″×11.5″ and A4. However, when printing on a non-standard page size or custom media, such known systems may produce undesired results.
To avoid these problems, printers, copiers, multi-function devices, and the like, often include a multiple purpose tray (MPT), i.e., the tray that folds up into the front of the printer which usually only holds about 100 sheets of paper. This tray is sometimes also referred to as a “by-pass tray”. Most often, custom media is only received into the printer from the MPT. Custom media, may be of any type of substantially flat material. For example, custom media may include paper, card stock, transparencies, Mylar, foils, fabrics, and the like. The MPT is unique in printers in that it is usually the only location where a user may load all media types, media sizes, custom media, as well as light and heavy weight media.
In a basic MPT there is often no size sensing capability. Rather, the user is required to manually enter the size of the media being loaded into the MPT via an input device usually located on a front panel of the printer. The problem with this method is that if the printer has a plurality of page size settings to choose from the user might have to scroll through all of the settings before selecting the desired paper size setting. Frequently the user does not select or enter the page size at all, but rather merely loads the media into the MPT and walks away from the printer. If the correct page size setting is not selected, then the printer will not run and the print job will remain unexecuted.
Custom media offers even larger problems in that a user often must input the actual dimensions of the media. Thus, not only is the user not likely to enter the media dimensions, if the user does try to enter the dimensions, the user often must enter the dimensions in a format other than the format known to the user resulting in the user being required to convert dimensions from a known format to an unknown format. For example, many users have difficulty converting known fraction dimensions into decimal units and vice versa.
Having an incorrect media size setting selected, or entering an incorrect dimension, can result in printers printing outside the intended print area. Ink that is not transferred to the media remains in the printer where it can do damage to the printer or spoil future printouts.